For the cake, grease two 9-inch (23-cm) round baking pans with baking spray. Line bottoms with parchment paper.

Preheat oven to 350°F (180°F).

In a large mixing bowl, whisk flour, baking powder, baking soda and salt. In a separate mixing bowl, whisk eggs, sugars, zest, rosemary and vanilla until smooth. Whisk in oil.

Using a silicone spatula, stir wet mixture into dry until just combined. Fold in parsnips and apples until evenly distributed.

Divide batter between pans and smooth out evenly with spatula.

Bake on middle rack until a toothpick inserted in the center comes out clean, 30 to 35 minutes. Cool cakes completely.

To make the frosting, place lemon zest, cream cheese and butter in bowl of a stand mixer fitted with a paddle. Beat on medium speed until smooth, stopping to scrape down bowl, about 1 minute. Reduce speed to medium-low. Gradually add icing sugar until just combined. Cover and refrigerate 30 to 45 minutes.

Remove parchment paper from cake layers. Place 1 layer on a platter. Spread top with half of frosting. Place other layer on top. Spread top with remaining icing. Garnish with rosemary, if desired.

In a medium bowl, beat together cream cheese and butter until smooth. Sift in cocoa powder, vanilla extract, salt and cream. Beat on low speed until the cocoa powder is incorporated, then increase speed to high, until very well combined. Sift in icing sugar, 1/2 cup at a time, beating slowly after each addition to incorporate. Increase speed to high and beat until smooth and light, about 3 minutes. Transfer dip to a serving dish and smooth top with a spatula.

Spread crushed chocolate cookies over the top of dip to form “dirt.” With decorating icing, write “RIP” on vanilla wafer cookies, then stand upright in dip to form “tombstones.” Serve with graham crackers, sliced apples and/or pretzels as desired.